Add third_party/pexpect

third_party/pexpect/doc/api/replwrap.rst

+replwrap - Control read-eval-print-loops
+========================================
+
+.. automodule:: pexpect.replwrap
+
+.. versionadded:: 3.3
+
+.. autoclass:: REPLWrapper
+
+   .. automethod:: run_command
+
+.. data:: PEXPECT_PROMPT
+
+   A string that can be used as a prompt, and is unlikely to be found in output.
+
+Using the objects above, it is easy to wrap a REPL. For instance, to use a
+Python shell::
+
+    py = REPLWrapper("python", ">>> ", "import sys; sys.ps1={!r}; sys.ps2={!r}")
+    py.run_command("4+7")
+
+Convenience functions are provided for Python and bash shells:
+
+.. autofunction:: python
+
+.. autofunction:: bash